1. Field of the Invention
This invention relates to a single lens reflex camera having a metering device, and more particularly, to a light-receiving device for use with an exposure meter in such camera.
2. Description of the Prior Art
In a single lens reflex camera, it is known to provide a translucent portion in part of a principal mirror that reflects light passing through the objective lens of the camera toward a finder optical system, and to use a reflecting-condensing member to cause the light passing through the translucent portion to be condensed upon a photoelectric converter element provided at the bottom of a mirror box.
On the other hand, even in the so-called center-weighted metering system, whereby a substantially wide range on the picture plane is metered, two systems have been proposed to reduce the size of the photoelectric converter element and to permit such element to be disposed outwardly of the path of the metering light beam so as not to intercept such light beam, i.e., to dispose the photoelectric converter element at the mirror box bottom with sufficient space from the reflecting-condensing member. The first system employs a concave or a convex mirror of low curvature as the reflecting-condensing member so that a large conjugate image of the metering portion of the picture plane is formed as an aerial image at a location spaced from the reflecting-condensing member, whereby the aerial image is reduced in size by an image-forming lens and is directed to the photoelectric converter element. The second system employs as the reflecting-condensing member, a concave mirror of high curvature so that a small conjugate image is formed as an aerial image in the vicinity of the concave mirror, whereby this image is directed to the photoelectric converter element by an image-forming lens.
However, both of these systems embody a disadvantage in that they require the image-forming lens to be of large diameter and, accordingly, require the light-receiving device to be of large size.
More particularly, according to the first method, the aerial image itself is large in size and necessarily, the image-forming lens receiving the light therefrom must be of large diameter; while, according to the second method, a light beam ranging over a great angle is condensed on the aerial image so that a light beam ranging over a great angle is also emitted from the aerial image and therefore, the image-forming lens must be of a larger diameter in order for it to receive all of the emitted light.